This invention relates to a disk player. Several kinds of disks have recently been developed and used, which are very often called digital audio disks (DADs). Compared with conventional audio disks which are used to store analog signals, DADs are capable of storing a greater quantity of data as recorded digital signals but produce less noise at the time of playback.
A disk player for replaying DADs is equipped with a clamp mechanism for firmly clamping the DAD on its turntable because the DAD is rotated at a speed very much higher than that at which the conventional audio disk is turned. FIG. 1 shows the principal portion of a clamp mechanism and a turntable installed in a conventional disk player.
As shown in FIG. 1, an annular boss 2 is formed over the whole outer periphery of a disk-shaped turntable 1, which abuts a recording disk 3 with its annular boss 2. On the other hand, an annular boss 5 is also formed on the outer periphery of a disk-shaped presser member 4 and is used to abut the lower principal surface of the recording disk 3. The presser member 4 is the principal component of a clamp mechanism and clamps the disk is cooperation with the turntable 1. The diameters of both the annular bosses 2 and 5 are almost the same.
The presser member 4 is rotatably supported by a support member 6 through a ball bearing 7, the support member 6 being vertically movable relative to the turntable 1. A guide 8 fitted into the center hole of the disk 3 for use in positioning the disk 3 on the turntable 1. The guide 8 protrudes around the center of rotation of the turntable 1. A recess 9 perpendicular to the central axis of rotation of the turntable 1 and circular in cross section is formed in the guide 8. A columnar projection 10 that can fit into the recess 9 is formed at the center of rotation of the presser member 4. The recess 9 and the projection 10 constitute a centering means for centering the presser member 4 relative to the turntable 1.
In the disk player thus constructed, a gap e is provided between the recess 9 of the turntable 1 and the projection 10 of the presser member 4, as shown in FIG. 1, to smooth the centering of the presser member 4 about the turntable 1. In the worst case, accordingly, the center axis of the presser member 4 is displaced from the central axis of rotation of the turntable 1 by a distance of e/2, thus causing the bearing member 7 to roll in the form of a circle having a diameter of e relative to the support member 6. Such deflection results in the accelerated degradation of the bearing 7 and causes the turntable 1 to oscillate in the radial direction because of uneven centrifugal force. Also the disk 3 can flex about the circumferential fulcrum between the two bosses 2 and as a result, it is not always possible to provide conditions under which smooth data reading is ensured by means of a pickup.